1. Field of the Invention
The present application related to a method to tune an emission wavelength of a semiconductor laser diode (hereafter denoted as LD).
2. Related Background Arts
It is known that an LD may tune an emission wavelength by being combined with an etalon filter. Because an etalon filter has a periodic transmission spectrum, an apparatus of an LD with an etalon filter detects an intensity of light emitted from the LD and transmitted through the etalon filter. The emission wavelength of the LD is tuned by feeding the detected intensity back to a temperature of the LD. This method may tune the emission wavelength of the LD with an extreme accuracy.
A Japanese patent application published as JP-2002-374033A has disclosed an optical signal source having variable emission wavelength. Another Japanese patent published as JP-2006-216860A has disclosed an apparatus to control an emission wavelength in a range shorter than a period of transmission spectrum of an etalon filter.